It is known in the art, pertaining particularly to vehicle engines, to actuate the valves by a crankshaft driven camshaft having cams which actuate valve lifters either directly or through a suitable valve train. The lifters normally actuate the intake and exhaust valves once each cylinder cycle.
In order to improve fuel efficiency or performance, some engines are provided with valve deactivation lifters, or valve lift profile switching lifters. When actuated, these switching lifters may shut off the valves of the selected cylinders so that the engine runs more efficiently on the other cylinders, which are maintained in operation. In some cases, switching lifters may be used to switch between high and low valve lift operation.
Engines having switching lifters may also be provided with one or more cam phasers, which are generally mounted on the camshafts, and are operated to advance or retard the timing of valve actuation of the intake and/or exhaust valves of the engine. Such cam phasers may be operated by hydraulic vane motors, built into the cam phasers, which rotate the angle of an associated camshaft relative to a driving sprocket in order to change the phase angle of the camshaft relative to the crankshaft phase angle.
The cam phasers may have hydraulic advance and retard drive chambers located within pockets in a drive sprocket and separated by vanes or legs projecting from a rotor mounted on the camshaft. The sprocket drives the camshaft by exerting rotation force or torque on the oil in the advance chambers and the oil acts against the vanes to rotate the camshaft. To change the camshaft phase angle, oil is shifted in or out of the advance chambers to the retard chambers on the other sides of the vanes so that the rotor is rotated, or changed in angle, relative to the drive sprocket.